One-Dimensional Looped Chain and Two-Dimensional Square Grid Coordination Polymers: Encapsulation of Bis(1,2,4-Triazole)-trans-cyclohexane into the Voids

Article abstract of DOI:10.1002/ejic.201801138

Two new coordination polymers [Cu(btzx)₂(MeOH)₂](NO₃)₂ (1) and [Cu(btrcy)₂(H₂O)₂](ClO₄)₂·btrcy (2) have been synthesized by reacting two bis-triazole/tetrazole-ligands namely m-xylylene-bis(tetrazole) (btzx) and bis(1,2,4-triazole)-trans-cyclohexane (btrcy) with Cu(NO₃)₂ and Cu(ClO₄)₂ respectively in a 1:3 metal/ligand ratio. These compounds are shown to form X-ray quality single-crystals under different conditions, and the crystal structures have been determined by single-crystal X-ray diffraction (SXRD). The SXRD data analysis revealed that 1 and 2 are 1D looped chain and 2D-square grid coordination polymers, respectively. More interestingly, the 2D-square grid architecture in 2 acts as an excellent host for the large guest ligand molecule btrcy, which is encapsulated within the voids of the 2D coordination polymer.

Full text of DOI:10.1002/ejic.201801138

DOI: 10.1002/ejic.201801138
Full Paper
Self-Assembly
One-Dimensional Looped Chain and Two-Dimensional Square
Grid Coordination Polymers: Encapsulation of Bis(1,2,4-Tri-
azole)-trans-cyclohexane into the Voids
Nayarassery N. Adarsh,[a] Marinela M. Dîrtu,[a] Philippe Guionneau,[b,c] Eamonn Devlin,[d]
Yiannis Sanakis,[d] Judith A. K. Howard,[c] Basab Chattopadhyay,[e] and Yann Garcia*[a]
Abstract: Two new coordination polymers [Cu(btzx)2(MeOH)2]- crystal structures have been determined by single-crystal X-ray
(NO3)2 (1) and [Cu(btrcy)2(H2O)2](ClO4)2·btrcy (2) have been syn- diffraction (SXRD). The SXRD data analysis revealed that 1 and 2
thesized by reacting two bis-triazole/tetrazole-ligands namely are 1D looped chain and 2D-square grid coordination polymers,
m-xylylene-bis(tetrazole) (btzx) and bis(1,2,4-triazole)-trans- respectively. More interestingly, the 2D-square grid architecture
cyclohexane (btrcy) with Cu(NO3)2 and Cu(ClO4)2 respectively in in 2 acts as an excellent host for the large guest ligand mol-
a 1:3 metal/ligand ratio. These compounds are shown to form ecule btrcy, which is encapsulated within the voids of the 2D
X-ray quality single-crystals under different conditions, and the coordination polymer.
Introduction
Notwithstanding of these pioneering examples, control over
the synthesis and applications of 2D materials based on CPs
still remains a significant research challenge. 2D CPs can be
synthesized by spontaneous supramolecular assembly of metal
ions and multi-dentate ligands such as for instance bis-carb-
oxylate, bis-pyridyl and bis-azole. The final supramolecular to-
pology is however highly controlled by several factors such as
metal/ligand ratio, solvent of crystallization, nature of the li-
gand, and the oxidation states of metal centers.[10] It is evident
from various reports that the nature of ligand is of great impor-
tance for the creation of 2D CPs.[11]
MOFs or CPs derived from azole ligands, so called metal-
azole frameworks (MAFs), in particular bis-triazole/tetrazole li-
gands, are still poorly explored.[12] As a part of our ongoing
research on the synthesis of novel MAFs, we are fascinated in
studying the supramolecular structural diversities of these coor-
dination networks and their driving forces (e.g. H-bonding, an-
ions, ligating topology, etc.) in relationship with their functional
properties (e.g. spin- crossover behavior, sorption properties,
etc.).[13] We have previously reported remarkable three dimen-
sional chains of nanoballs derived from Cu(BF4)2 and 2-(4H-
1,2,4-triazol-4-yl)acetic acid. The crystal structure analysis re-
vealed that the self-assembly of the C3-symmetric, μ3-O
bridged triangular tricopper SBU is the main driving force for
the formation of nanoballs with a void size of ca. 1 nm and
total solvent accessible volume of 4477.5 Å3, which accounts
for 48 % of the cell volume.[13a] We have also described a novel
chiral helicate, derived from a triazole-carboxylate ligand and
CdCl2,[13b] and more recently an unprecedented single walled
CuII metal organic nanotube able to entrap metallic mercury.[14]
With the aim to obtain new porous 2D CPs, we explore two
bis-azole ligands and their supramolecular assembly with CuII.
Furthermore, such ligands might exhibit an inter network
supramolecular recognition property, which, in turn, might
Coordination polymers (CPs) or metal-organic frameworks
(MOFs) have attracted considerable attention in recent years
due to their diverse pore sizes, shapes, topologies, and unprece-
dented internal surface areas that can be appropriate for in-
triguing applications.[1] Recently two dimensional coordination
polymers (2D CPs) become popular in material science, not only
due to their rich synthetic chemistry, chemical flexibility and
the presence of metal ions that enhance novel optical, mag-
netic and electrical properties, but also due to their interesting
nano-structure (nanosheet) and the resultant applications.[2] In
fact these 2D materials are not much explored, despite of some
examples where it showed remarkable applications in bio-
mimetic enzymes,[3] molecular sieves membranes,[4] gas separa-
tion[5] catalysis[6] and photoluminescence.[7] Recently we re-
ported a 2D corrugated sheet coordination polymer derived
from FeII and a tris-tetrazole ligand, which showed remarkable
spin crossover phenomena[8] in both bulk single crystals and in
exfoliated nanosheets.[9]
[a] Institute of Condensed Matter and Nanosciences, Université catholique de
Louvain,
Place L. Pasteur 1, 1348 Louvain-la-Neuve, Belgium
E-mail: yann.garcia@uclouvain.be
https://ygarcia.homestead.com/
[b] CNRS, Univ. Bordeaux, ICMCB, UMR 5026,
87 avenue du Dr. A. Schweitzer, 33608 Pessac, France
[c] University of Durham, Department of Chemistry,
South Road, Durham, DH1 3LE, UK
[d] Institute of Nanoscience and Nanotechnology, NCSR Demokritos,
Athens 15310, Greece
[e] Dr. Basab Chattopadhyay
Department of Physics, Norwegian University of Science and Technology
(NTNU),
Hogskoleringen, 7491 Trondheim, Norway
Supporting information and ORCID(s) from the author(s) for this article are
available on the WWW under https://doi.org/10.1002/ejic.201801138.
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leads to the formation of more robust supramolecular host ar- reasonable yield (53 %) of [Cu(btzx)2(MeOH)2]·(NO3)2 (1). The
chitectures and ensure guest encapsulation within the intersti- synthesis of btrcy was inspired from the patented procedure of
tial voids supported by intermolecular interactions.[15,16] The in- Bayer et al.[20] Reaction of btrcy with Cu(ClO4)2·6H2O in water
tegration of host molecules within the voids of the coordination in
a 1:3 ratio and 1:2 afforded a blue precipitate of
cages, lead to the encapsulation of interesting molecules, ex- [Cu(btrcy)2(H2O)2](ClO4)2·btrcy (2) and [Cu(btrcy)2(H2O)2]-
tremely relevant to the development of useful chemotherapeu- (ClO4)2 (3), respectively. While the blue precipitate of 2 was re-
tic drugs.[17] The azole based ligand molecules attracted many crystallized from water/acetone solution as dark blue colored
researchers owing to their potential applications in medicinal single crystals under slow evaporation over a week time, 3 did
chemistry.[18]
not produce any crystals, under identical conditions. Attempts
to recrystallize 3, from different aqueous solution mixtures like
water/methanol, water/ethanol, water/THF, water/1,4-dioxane,
water/DMF, water/DMSO, were unsuccessful. Repeated synthe-
sis with immediate filtration starting from a 1:2 ratio afforded a
blue precipitate of [Cu(btrcy)2(H2O)2]·(ClO4)2 (3). FT-IR spectra
of btzx and btrcy contain characteristic bands at 3116 and
3124 cm–1, corresponding to C–H fragments of the tetrazole
and triazole groups, respectively. FT-IR spectra of 1 and 2 each
contain a broad band for the water and methanol molecules
centered at 3390–3400 cm–1. A band for the tetrazole and tri-
azole CH groups was found at 3122 and 3112 cm–1 in the spec-
tra of 1 and 2, respectively. The nitrate counter anions were
detected at 1382 cm–1 in 1.
Thus in order to obtain 2D CPs having encapsulated azole
ligands, we deliberately reacted the rigid bis-1,2,4-triazole li-
gand btrcy and flexible bis-tetrazole ligand btzx with CuII
[Cu(ClO4)2·6H2O with btrcy and Cu(NO3)2·3H2O with btzx] in
1:2 and 1:3 metal/ligand stoichiometric ratio (Scheme 1).
Scheme 1. Chemical structure of the azole ligands used in this work.
Crystal Structures
Single crystal X-ray diffraction (SXRD) analysis of 1 revealed that
it belongs to the triclinic P1¯ space group (Table 1). The asym-
metric unit comprises a CuII, one molecule of ligand btzx and
methanol – both being coordinated to the CuII metal center
Results and Discussion
Synthesis and Spectroscopic Characterization
The btzx molecule was synthesized by following a previously and a nitrate counter anion. The CuII center displayed a slightly
reported procedure.[19] Reaction of btzx with Cu(NO3)2·3H2O in distorted square bipyramidal geometry [N–Cu–N = 88.89(7)–
1:3 or 1:2 metal/ligand ratio, separately in methanol solution 91.11(7)°, ∠N–Cu–O = 85.79(6)–94.21(6)°] (Table 2); the equato-
lead to pale-green block shaped X-ray quality single crystals in rial positions of the metal center are coordinated by tetrazole
Table 1. Crystal data.
Crystal data
1
2
Empirical formula
Formula weight
Crystal size [mm]
Crystal system
Space group
a [Å]
b [Å]
c [Å]
α [°]
ꢀ [°]
C22H28CuN18O8
736.16
0.30 × 0.25 × 0.22
Triclinic
C15H23ClCu0.50N9O5
476.64
0.08 × 0.04 × 0.02
Triclinic
P1
P1
¯
¯
8.6210(18)
10.0631(17)
10.2123(11)
81.089(12)
71.498(14)
65.929(18)
766.8(2)
6.5086(4)
12.4962(8)
12.9374(8)
102.423(3)
94.894(3)
92.474(3)
1021.80(11)
2
1.549
495
0.743
293(2)
γ [°]
Volume [Å3]
Z
1
Dcalcd. [g/cm3]
F(000)
1.594
379
0.791
150(2)
μ Mo-Kα [mm–1
T [K]
]
Range of h, k, l
θmin/max
Reflections collected/unique/observed
Data/restraints/parameters
Goodness of fit on F2
–10/10, –12/12, –12/12
2.92/25.99
8369/2966/2859
2966/0/225
1.066
8/–9, 15/–17, 18/–18
1.619/30.371
8296/5363/3674
5363/0/313
1.020
Final R indices [I > 2σ(I)]
R indices (all data)
R1 = 0.0323, wR2 = 0.0763
R1 = 0.0342, wR2 = 0.0776
R1 = 0.0621, wR2 = 0.1275
R1 = 0.1039, wR2 = 0.1481
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N atoms and the apical positions are occupied by a methanol sustained by various intermolecular interactions (Figure 1b). It
molecule. The extended coordination of the bis-tetrazole ligand is revealed from the overall packing of the looped chains along
(btzx) leads to the formation of a 1D looped chain coordination the crystallographic axis “a” that the template effect of the
polymer (Figure 1a). The polymeric chains recognize the coun- nitrate anion is one of the crucial factors for the formation of
ter anion via O–H···O hydrogen bonding involving the metal such chains in 1 (Figure 1c).
bound methanol molecule and the counter anion nitrate
[O···O = 2.696(5) Å; ∠O–H···O = 172.52°] (Figure 1a). Such chains
are packed on top of each other in a slightly off-set fashion
Compound 2 also crystallizes in the centrosymmetric triclinic
space group P1¯ (Table 1) The asymmetric unit (Figure 2a) con-
tains one perchlorate anion, one ligand molecule (btrcy) cen-
tered on the (1/2, /2, /2) site and one CuII ion situated at the
crystallographic cell origin and bonded to two ligands moieties
and a water molecule. Each entity is generated in its entirety
by the corresponding inversion centers. The unit cell content is
Cu(C10H14N6)2(H2O)2·2(ClO4)·C10H14N6. Thus, each CuII ion which
is linked to four ligands and two water molecules (Figure 2b) is
surrounded by four N and two O atoms. Such a coordination
environment of the CuII adopts the shape of a square bipyramid
geometry which is defined by only two Cu–N distinct bond
lengths [Cu–N4 = 2.014(2) Å and Cu–N1 = 2.035(2) Å], one Cu–
O bond length [Cu–O1 = 2.431(3) Å] and the corresponding
angles [N4–Cu–N1 = 89.42(9)°, N4–Cu–O1 = 85.20(10)° and N1–
Cu–O1 = 91.53(11)] (Table 2). The CuII atoms are bridged by
the ligands creating a polymeric structure in a two dimensional
network (Figure 2b). The boughs formed by the ligands which
link the copper atoms within a same layer are parallel to the
[110] or to the [101] directions so as the 2D sheets are parallel
to the (–111) crystallographic plane (Figure 2c). As a result, the
shortest Cu···Cu separations do not bring into play copper at-
oms from a same layer: the interlayer Cu···Cu shortest separa-
tions correspond to the a [6.5086(4) Å], b [12.4962(8) Å] and c
[12.9374(8) Å] cell parameters and the intra-layer Cu–Cu short-
1
1
Table 2. Selected bond lengths and bond angles associated with the coordi-
nation spheres of 1 and 2.
Bond length [Å] Bond length [Å] Bond angle [°]
1
Bond angle [°]
Cu(1)–N(2)
Cu(1)–N(18)
Cu(1)–O(32)
2.0308(16)
2.0659(17)
2.2535(14)
N(2)–Cu(1)–N(2)
N(2)–Cu(1)–N(18)
N(2)–Cu(1)–N(18)
N(18)–Cu(1)–N(18)
N(2)–Cu(1)–O(32)
N(2)–Cu(1)–O(32)
N(18)–Cu(1)–O(32)
N(18)–Cu(1)–O(32)
180.02
91.11(7)
88.89(7)
179.998(2)
93.66(6)
86.34(6)
85.79(6)
94.21(6)
2
Cu(1)–N(1)
Cu(1)–N(4)
Cu(1)–O(1)
2.036(2)
2.013(2)
2.432(3)
N(1)–Cu(1)–O(1)
N(1)–Cu(1)–O(1)
N(4)–Cu(1)–N(1)
N(4)–Cu(1)–N(1)
N(4)–Cu(1)–O(1)
N(4)–Cu(1)–O(1)
O(1)–Cu(1)–O(1)
N(4)–Cu(1)–N(4)
N(1)–Cu(1)–N(1)
91.53(11)
88.47(11)
90.56(10)
89.44(10)
85.17(11)
94.83(11)
180.02
180.02
180.02
Figure 1. Crystal structure illustration of 1; a) the looped chain CP in 1; the
hydrogen bonding interaction involving the nitrate anion and metal bound
MeOH also displayed; b) offset packing of the looped chains supported by
various hydrogen bonding and other weak interactions; c) occlusion of nitrate
anion within the cavities of the lopped chain CP.
Figure 2. Crystal structure illustration of 2; a) asymmetric unit of 2; b) the
square grid architecture in 2; c) stacking modes of the square grids [adjacent
grids are shown with orange (space-fill) and black (wireframe)]; occlusion of
perchlorate anions and ligand molecules within the channels sustained by
hydrogen bonding are also displayed.
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est distances corresponds to the diagonal of the (ab) and (ac)
planes [13.838(1) Å and 13.978(1) Å, respectively]. The average
planes of the triazole entities from the same bough are all paral-
lel for symmetrical reasons while the angle between the aver-
age plane of each triazole entity that belongs to a bough paral-
lel to [101] and the average plane of a triazole entity that be-
longs to a bough parallel to [110] is 167.4(1)°. The sheets are
stacked along the direction and are deduced from each other
by a simple period translation, which results in the formation
of real channels (Figure 2c). The shape of the section of such
tubes is almost a square with a surface of around 195 Å2.
These tubes can also be seen as infinite chains of cavities
delimited by the ligands boughs, the volume of the cavities
being, for symmetrical reasons, equal to the volume of the crys-
tallographic cell (1022 Å3). Interestingly, one molecule of azole
ligand and two perchlorate anions were encapsulated in these
cavities (Figure 2c) supported by various H-bonding. The layers
are linked to the guest molecules by H-bonding between the
water molecules and the nitrogen atoms of the ligand
[O1···N8 = 2.855(1) Å, H1A···N8 = 2.01(1) Å, O1–H1···N8 =
169(1)°] and between the ligands and the perchlorate anions
[C2···O3 = 3.400(7) Å, H2···O3 = 2.527(5) Å, C2–H2···O3 =
157(1)°]. The perchlorate anions are also involved in H-bonding
with the ligand molecules with the same cavity [C11–O5 =
3.370(5) Å, C11–H11···O5 = 169.8(3)°]. No relatively short distan-
ces are created between neighbouring cavity contents. The
crystal structure of 2 differs from the crystal structures of two
reported layered CuII based polymeric structure with bridging
bis-triazole-alkane ligands.[21] Indeed in the latter case the
stacking mode prevents from the formation of channels within
the crystals while in the present case such channels are gener-
ated and are filled with guest molecules and anions. Note that
the crystal structure was also determined at 150 K but no
changes were observed.
Figure 3. a) FT-IR comparison plot (blue: free ligand btzx; red and green:
blue crystals obtained from 1:2 and 1:3 metal salt/btzx stoichiometric ratio,
respectively); b) the optical microscope image of 1; c) FE-SEM image of 1; d)
PXRD comparison plot under various conditions (red: simulated; magenta:
obtained from 1:2 and 1:3 metal salt/btzx stoichiometric ratio, respectively).
The Effect of Metal/Ligand Ratio on the Formation of 2D
CPs
We studied the effect of metal/ligand stoichiometric ratio on
the structure of CuII CPs derived from btzx and btrcy, in order
to study the effect of metal/ligand ratio on the formation of
2DCPs. The reaction of btzx with Cu(NO3)2 in 1:2 and 1:3 exclu-
sively resulted in pale blue single crystals (Figure 3b). FT-IR anal-
ysis of the blue single crystals obtained from each reaction re-
vealed that both belong to 1D chain CP 1; the FT-IR showed
identical peaks: the band at 1378 cm–1, attributed to the
stretching N–O of the nitrate anion and the Figure print region
of both samples showed identical peak position (Figure 3a). The
scanning electron microscopy (SEM) image shown a fibrous
morphology in these crystals (Figure 3c). Powder X-ray diffrac-
tion (PXRD) patterns of the crystalline products isolated from
1:2 and 1:3 stoichiometric experiments performed at the syn-
thetic conditions of 1 match well with that of the simulated
XRPD patterns obtained from the corresponding single crystal
data, indicating the formation of 1, irrespective to the metal/
ligand ratio (Figure 3d).
Figure 4. a) FT-IR comparison plot of 2, 3 and btrcy; b) optical microscope
image of crystals of 2; c) and d) SEM image of 2 and 3, respectively; e) PXRD
comparison plot (blue: bulk crystals of 2, red: simulated of 2, magenta: bulk
powder of 3).
In contrast to 1, the starting reaction stoichiometry of 1:2
and 1:3 (metal/ligand) in synthesizing compound 2 turn out to
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be two different crystalline phases. While the 1:2 metal/ligand where ꢀ is the Bohr magneton. The first term describes the
ratio resulted in a microcrystalline blue powder, the 1:3 metal/ Zeeman interaction and the second term the hyperfine interac-
ligand ratio lead to the formation of blue plate shaped single tion between the electronic S = 1/2 and the nuclear I = 3/2 spin
crystals (Figure 4b). FT-IR comparison plot confirmed that the of the 63/65Cu nucleus. The spectra can be simulated with the
blue powder and single crystals were chemically similar (with following parameters:gs = 2.31(1), g⊥ = 2.08(1), As = 481(5)
same functional groups and chemical entities) (Figure 4a). FT-IR MHz, A⊥ = 37(5) MHz. In order to account for the particular
spectra showed identical peaks: the band at 1258 cm–1, attrib- lineshape, a distribution on the g-tensor components was used
uted to the stretching N–O of the nitrate anion and the Figure with σgs = 0.22 and σg⊥ = 0.21 and an intrinsic linewidth of
print region of both samples showed identical peak positions 4.4 mT. From the determined g-tensor components from the
(Figure 4a). Morphological characterization by FE-SEM revealed analysis of the EPR spectra the parameter
the presence of nanoparticles and block shaped crystals, from
the products (blue powder and blue crystals) obtained from 1:2
and 1:3 (metal/ligand ratio), respectively (Figure 4c and 4d). Fi-
nally PXRD data confirmed that the microcrystalline blue pow-
der and single crystals belong to two different crystalline pha-
ses (Figure 4e). While PXRD revealed that samples containing
blue single crystals exhibit the same crystalline pattern that of
the simulated pattern of 2 from the SXRD data, the blue micro-
crystalline powder showed a different XRD pattern. Indexing of
the powder diffraction pattern of this powder using the
program DICVOL06[22] showed triclinic unit cell having the cell
parameters, a = 13.36(1), b = 13.97(2), c = 13.35(2) Å; α =
62.38(1), ꢀ = 98.2(1), γ = 101.4(1)°; V = 2159.14 Å3, (Figure S1
in the Supporting Information). Thus from FT-IR, PXRD and SEM
it is confirmed that the blue powder and single crystals ob-
tained from the reaction of Cu(ClO4)2 and btrcy in 1:2 and 1:3
stoichiometric ratio, respectively are chemically identical, al-
though their crystalline phases are different. Elemental analysis
of blue powder and single crystals indicates the metal/ligand
ratio of 1:2 and 1:3, respectively. Thus, we propose the formula-
tion of the blue powder 3 as [Cu(btrcy)2(H2O)2](ClO4)2.
is obtained which is in agreement with the g value determined
from the magnetic susceptibility measurements. Overall, the
combined magnetic measurements studies and EPR spectro-
scopic data for 1 are consistent with magnetically isolated CuII
ions.
Magnetic Studies
From the crystal structure, 1 can be considered as a 1D looped
chain, in which CuII ions are linked by the large ligand btzx.
In Figure 5a we showed the temperature dependence of the
magnetic susceptibility from a powder sample of 1. At room
temperature ꢀMT = 0.47 cm3 mol–1 K. This value is close to the
value expected for an S = 1/2 system with g > 2.0. As the tem-
perature decreases, ꢀMT decreases slightly, reaching a value of
0.44 cm3 mol–1 K at 5 K. The temperature dependence of ꢀM
can be adequately modelled with the Curie law for an S = 1/2
system,
with g = 2.16, and including a Temperature Independent
Paramagnetism (TIP) contribution of 9.8 × 10–5 cm3 mol–1. The
field dependence of magnetization at 5 K (inset of Figure 5a)
follows the Brillouin function for an S = 1/2 system with g =
2.16 further indicating negligible intermolecular interactions. In
Figure 5b we show the room temperature X-band EPR spectrum
from a powdered sample of 1. The spectrum is typical for an
isolated CuII ion with axial properties (gs > g⊥) and can be simu-
lated with the spin Hamiltonian:
Figure 5. a) Temperature dependence of ꢀMT in the presence of a magnetic
field of 0.1 T from a powdered sample of 1. Solid line is a simulation with
the parameters shown in the text. Inset: The dependence of magnetization
on the magnetic field at 5 K. b) Experimental (black line) and theoretical (red
line) X-band EPR spectra from a powder sample of 1 at room temperature.
EPR conditions: microwave power, 2.0 mW; modulation amplitude, 10 Gpp;
microwave frequency, 9.42 GHz.
No magnetic studies were performed on the grids 2 and 3,
due to their expected paramagnetic behavior favored by long
metal–metal distances (≈ 13.8 Å in 2).
H = ꢀB g S + I A S
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Synthesis of Coordination Polymers 1–3
Conclusions
[Cu(btzx)2(MeOH)2]·(NO3)2 (1) was synthesized by layering a meth-
anolic solution of btzx (50 mg, 0.2064 mmol) over an aqueous solu-
tion of Cu(NO3)2·3H2O (8.5 mg, 0.047 mmol) in water and future
layering of a methanolic solution of Cu(NO3)2 (25 mg, 0.1032 mmol).
The resultant bi-layer solution, thus obtained, was kept undisturbed.
After two days, pale-blue block shaped X-ray quality crystals were
obtained. Yield: 40 mg (53 %). C22H28CuN18O8 (736.12): calcd. C
35.90, H 3.83, N 34.25; found C 35.76, H 4.20, N 34.18. FT-IR (KBr):
In summary, we have explored bis-azole based, ditopic ligands
(btzx and btrcy) to search for a 2D CP having an octahedral
metal center, and its capability for encapsulation of organic li-
gands. The tetrazole ligand btzx showed 1D CP structure in 1,
while polymerized with CuII. The NO3– anion acts as a template
–
(the NO3 anion got entrapped within the cavity of the looped
chain CP in 1). On the other hand, the triazole ligand btrcy
displays a 2D CP structure in CP 2. Interestingly, the voids of
the 2D square grid structure in 2 are used for the encapsulation
ν = 3466 (br. s, MeOH O–H stretch), 3091 (br. s, tetrazole C–H
˜
stretch), 3064 (w, aromatic C–H stretch), 1587 (s), 1548 (s), 1479 (s),
1429 (s), 1378 (s, nitrate N–O stretch), 1290 (s), 1246 (s), 1193 (m),
1168 (m), 1145 (m), 1128 (w), 1109 (w), 1082 (m), 964 (m), 931 (m),
810 (s), 731 (s), 719 (s), 694 (s), 665 (m), 648 (m), 605 (m), 594 (m),
–
of btrcy molecules and ClO4 anions, supported by hydrogen
bonding interactions.
578 (m) cm–1
.
[Cu(btrcy)2(H2O)2](ClO4)2·btrcy (2): The btrcy molecule (0.19 g,
0.872 mmol) dissolved in hot water (20 mL) was added to a solution
of [Cu(H2O)6](ClO4)2 (0.14 g, 0.291 mmol) in water (20 mL). The solu-
tion became turbid and a very fine blue precipitate appeared. The
volume of the solution was completed to 210 mL with 10 mL of
acetone and warmed to recrystallize the precipitate. The solution
was left to evaporate for two months at room temperature, after
which the volume of the solution was completed to 75 mL, and
warmed to 100 °C. This last procedure did not dissolve the precipi-
tate for which shining blue thin crystals were collected shortly after-
wards. These crystals were washed with a minimum amount of wa-
ter and dried in air. Yield: 20 mg (8 %). C30H46Cl2CuN18O10 (953.26):
calcd. C 37.8, H 4.86, N 26.45; found C 38.24, H 5.02, N 26.38. FT-IR
Experimental Section
Materials and Methods: All chemicals and solvents were commer-
cially available (Aldrich) and used without further purification. The
ligand m-xylylene-bis(tetrazole) (btzx) was synthesized by following
a reported procedure.[19] Elemental analysis was carried out at
MEDAC (UK) and in Vernaison CNRS. FT-IR spectra were recorded
on a Shimadzu Benelux FT-IR-84005 spectrometer using KBr discs
at room temp. between 4000 and 400 cm–1. Nuclear magnetic reso-
nance (NMR) spectra were recorded on a Bruker ARX-250 spectro-
photometer using [D6]DMSO as solvent. FE-SEM images were per-
formed on a scanning electron microscope (FEI Quanta 650 FEG) at
acceleration voltages of 5–10 kV. Powder X-ray diffraction (PXRD)
patterns were recorded on a PANalytical X′Pert PRO MRD (Cu-Kα
radiation, λ = 1.5406 Å) X-ray diffractometer.
(KBr): ν = 3442 (br. s, water O–H stretch), 3088 (br. s, triazole C–H
˜
stretch), 3062 (w, aromatic C–H stretch), 1502 (s), 1466 (s), 1418 (s),
1286 (s), 1232 (s), 1140 (m), 1122 (w), 1100 (w), 1072 (s, perchlorate
Cl–O stretch), 961 (m), 822 (s), 723 (s), 666 (m), 628 (m), 601 (m),
EPR: Room temperature X-band EPR spectra from a powdered sam-
ple of 1 were collected with an upgraded ER-200D Bruker EPR spec-
trometer, equipped with an Anritsu Frequency counter, and an NMR
Gaussmeter.
504 (m) cm–1
.
[Cu(btrcy)2(H2O)2](ClO4)2 (3): The btrcy molecule (0.19 g,
0.863 mmol) dissolved in hot water (20 mL) was added to a solution
of [Cu(H2O)6](ClO4)2 (0.160 g, 0.432 mmol) in water (20 mL). A dark
blue precipitate was obtained immediately, filtered, washed with
water and air dried. Yield: 220 mg (69 %). C20H32Cl2CuN12O10
(735.00): calcd. C 32.68, H 4.39, N 22.87; found C 33.12, H 5.04, N
Magnetism: Magnetic susceptibility measurements of 1 was per-
formed on a MPMS-5500 Quantum Design instrument in the tem-
perature range 5–300 K.
23.06. FT-IR (KBr): ν = 3441 (br. s, water O–H stretch), 3078 (br. s,
˜
Caution: Perchlorate and tetrazole compounds are potentially ex-
plosive. Although no problem was encountered in the present
study, care must be taken when handling such substances.
triazole C–H stretch), 3060 (w, aromatic C–H stretch), 1501 (s), 1469
(s), 1418 (s), 1286 (s), 1232 (s), 1141 (m), 1120 (w), 1101 (w), 1071
(s, perchlorate Cl–O stretch), 960 (m), 820 (s), 721 (s), 664 (m), 622
(m), 601 (m), 501 (m) cm–1
.
1,2-Bis(1,2,4-Triazol-4-yl)cyclohexane (btrcy): Freshly prepared
anhydrous formic hydrazide (2.104 g, 0.03503 mol) and triethyl-
orthoformate (6.97 mL, 0.0419 mol) in MeOH (40 mL) were heated
to reflux for 2 h, then trans-cyclohexane diamine (2 g, 0.01752 mol)
in anhydrous MeOH (15 mL) was added dropwise, and the mixture
was kept at reflux for a further 6 h. After removal of the solvent
under reduced pressure, a pale oily liquid obtained, which eventu-
ally solidified to a pinkish white residue. The residue formed was
removed by filtration and recrystallized from MeOH (10 mL) to af-
ford white crystalline material. Yield: 1.8 g (47 %). C10H14N6 (218.26):
calcd. C 55.03, H 6.47, N 38.50; found C 55.09, H 4.92, N 38.74. FT-
Single Crystal X-ray Diffraction Experiment: X-ray data collec-
tions of 1 were performed on a Mar345 image plate detector using
Mo-Kα radiation (rotation anode, multilayer mirror) at 120(2) K. The
data were integrated with the CrysAlisPro software.[23] The imple-
mented empirical absorption correction was applied. The structures
were solved by direct methods using the SHELXS-97 program[24]
and refined by full-matrix least-squares on |F2| using SHELXL-97.[24]
Non-hydrogen atoms were anisotropically refined and the hydrogen
atoms were placed on calculated positions in riding mode with
temperature factors fixed at 1.2 times Ueq of the parent atoms and
1.5 times Ueq for methyl groups.
IR (KBr): ν = 3444 (w), 3137 (m), 3107 (m), 3041 (w), 2965 (w), 1760
˜
(s), 1703 (s), 1521 (m), 1441 (m), 1399 (s), 1365 (m), 1346 (s), 1186
(s), 1118 (m), 1075 (m), 1030 (m), 969 (m), 810 (w), 726 (m), 531 (m), Single crystals of 2 appear as intense blue regular spearheads. A
1
631 (m) cm–1. H NMR (300 MHz, [D6]DMSO, 298 K): δ = 1.85–1.92 small single crystal was mounted on a glass fiber and positioned
(t, J = 9.0 Hz, 4 H), 2.17–2.19 (d, J = 6.0 Hz, 4 H), 8.64 (s, 4 H) ppm.
13C NMR (300 MHz, [D6]DMSO, 298 K): δ = 30.4, 34.8, 42.9, 123.6,
132, 134.5, 143, 168.5 ppm. HRMS: m/z calcd. for C13H13N4O2 [M +
H+]: 218.13, found 218.12.
on a Bruker smart CCD. After checking the quality of the diffraction
pattern from preliminary scans, a data collection was run at room
temperature. Considering the weakness of the Bragg peaks inten-
sity the detector was positioned as close as possible from the sam-
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Supporting Information (see footnote on the first page of this
article): Indexing data of 3 can be found in the Supporting informa-
tion.
Acknowledgments
This work was supported by the Fonds National de la Recherche
Scientifique-FNRS (PDR T.0102.15) and COST action CA15128.
M. M. D. is a chargé de recherches from the F.R.S.-FNRS (Bel-
gium). We thank the Belgian Science Policy and the Marie Curie
Actions from the European Commission for a postdoctoral re-
search fellowship allocated to N. N. A. E. D. and Y. S. acknowl-
edge support by the project MIS 5002567, implemented under
the “Action for the Strategic Development on the Research and
Technological Sector”, funded by the Operational Programme
“Competitiveness, Entrepreneurship and Innovation” (NSRF
2014-2020) and co-financed by Greece and the European Union
(European Regional Development Fund).
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Keywords: Coordination polymers · N ligands · Host-guest
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Received: September 19, 2018
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Self-Assembly
N. N. Adarsh, M. M. Dîrtu, P. Guionneau,
E. Devlin, Y. Sanakis, J. A. K. Howard,
B. Chattopadhyay, Y. Garcia* ......... 1–8
One-Dimensional Looped Chain and
Two-Dimensional Square Grid Coor-
dination Polymers: Encapsulation of
Bis(1,2,4-Triazole)-trans-cyclohex-
ane into the Voids
The spontaneous self-assembly of bis- grid (2), respectively. The grid architec-
azole ligands such as m-xylylene- ture in 2 acts as an excellent host for
bis(tetrazole) (btzx), and bis(1,2,4-tri- the large guest ligand molecule btrcy,
azole)-trans-cyclohexane (btrcy) with which was found encapsulated within
Cu(NO3)2 and Cu(ClO4)2 resulted in a the voids of the 2D coordination poly-
1D looped chain (1) and a 2D square mer.
DOI: 10.1002/ejic.201801138
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